So seriously, it didn't work out at all. We're using SliceHost (which, FYI, rocks) and we've been running a bit on the low side when it comes to system resources. I decided that I'd upgrade us to the next step this morning to increase performance and allow us to actually upgrade some important software. Everything seemed to be going okay right up until the point where it told me to check our slice. It simply wouldn't respond. No ping, no SSH, no web. I couldn't even open the console. I gave it about 10-15 minutes to come back up and still couldn't get anything, so I told it to revert back to the way it was.
About 5 minutes later, it said it was done. Still nothing. I frantically e-mailed support thinking I'd just bombed the whole website. About 20 minutes later (when they responded, no less), the server was back up in it's previous state. Expect, of course, I needed to rebuild PHP for Apache to start, another 15-20 minute delay. Finally, it was back up and running like it should be.
I'm thinking I'll try the upgrade again really late tonight so it'll have plenty of time to start meshing, so be prepared for more downtime around 10-11PM Mountain until whenever it's done.